How to limit rows for a table?

Question

Hi,
does anyone knows a good way to limit the number of rows for a table?
thanks
aldo

Answer 1

You can limit the number of rows using a trigger. Below is quick and dirty example that has not been fully tested.
test@ORCL> create table rowlimit (col1 number);
Table created.
Elapsed: 00:00:00.34
test@ORCL> create or replace trigger limit_rows
  2  before insert
  3  on rowlimit
  4  declare
  5    v_count number;
  6  begin
  7     select count(*)
  8     into v_count
  9     from rowlimit;
10
11     if v_count >= 4 then
12       raise_application_error(-20000, 'Table can have no more then 4 rows');
13     end if;
14  end;
15  /
Trigger created.
Elapsed: 00:00:00.09
test@ORCL> insert into rowlimit values(1);
1 row created.
Elapsed: 00:00:00.03
test@ORCL> insert into rowlimit values(2);
1 row created.
Elapsed: 00:00:00.00
test@ORCL> insert into rowlimit values(3);
1 row created.
Elapsed: 00:00:00.00
test@ORCL> insert into rowlimit values(4);
1 row created.
Elapsed: 00:00:00.00
test@ORCL> insert into rowlimit values(5);
insert into rowlimit values(5)
ERROR at line 1:
ORA-20000: Table can have no more then 4 rows
ORA-06512: at "TEST.LIMIT_ROWS", line 9
ORA-04088: error during execution of trigger 'TEST.LIMIT_ROWS'
Elapsed: 00:00:00.04
test@ORCL> commit;
Commit complete.
Elapsed: 00:00:00.00
test@ORCL> select count(*) from rowlimit;
  COUNT(*)
         4
Elapsed: 00:00:00.00
test@ORCL>